Recently, a user terminal (so-called dual terminal) having a cellular communication unit and a WLAN communication unit becomes popular. Moreover, WLAN access points (hereinafter simply referred to as “access points”) managed by an operator of a cellular communication system increases.
3GPP (3rd Generation Partnership Project), which is a standardization project of a cellular communication system, is planning to consider a technique capable of enhancing interworking between the cellular communication system and the WLAN system in a radio access network (RAN) level (see Non-patent document 1).
Then, one of the purposes of such technique is balancing the load level of cellular base stations and access points by increasing the usage rate of access points.
On the other hand, in order to achieve efficient access point discovery process performed by a user terminal, the standardization of ANDSF (Access Network Discovery and Selection Function) is currently in progress.
In ANDSF, an ANDSF server existing in a core network provides WLAN-associated information to a user terminal by a NAS (Non Access Stratum) message.